Hitherto, there have been mainly produced two types of golf balls. The one is a solid golf ball, such as a two-piece golf ball or a three-piece golf ball, which is composed of a core formed from integrally molded rubber material and a thermoplastic resin cover (e.g. ionomer resin cover) formed on the core. The other is a thread wound golf ball which is composed of a solid or liquid center, a thread rubber wound layer formed on the center and a cover of ionomer resin or balata (transpolyisoprene) etc. having a thickness of 1 to 2 mm covering on the thread rubber wound layer. In the solid golf ball, a two-piece solid golf ball is composed of a core and a cover, and has been commercially available since 1982, because of easiness of production and the like. The two-piece solid golf ball has better durability and better flight performance because of larger initial velocity at the time of hitting and longer flight distance, when compared with the thread wound golf ball. Therefore, the two-piece solid golf ball is generally approved or employed by many golfers, mainly by the average golfer.
On the other hand, the two-piece solid golf ball exhibits much harder shot feel at the time of hitting than the thread wound golf ball. Therefore, the two-piece solid golf ball is not approved nor employed by some users such as elderly persons or women who are less athletic. In order to improve shot feel, it has been attempted to soften the core by reducing the hardness of the core. The method improves the shot feel, while sacrificing flight distance, because the rebound characteristics are degraded.
Recently, the two-piece solid golf ball has been approved and employed by professional golfers or top amateur golfers, because the two-piece solid golf ball has excellent flight performance and uniformity of quality between golf balls. The professional golfers or top amateur golfers require not only good shot feel but suitable controllability. The ionomer resin, which has been generally used for cover materials of two-piece solid golf balls, shows high rigidity and high hardness, in order to impart sufficient flight performance and durability to the golf ball, and thus deteriorating controllability.
In order to solve the above problem, it has been proposed that a golf ball has a cover formed from a resin having low rigidity and low hardness. However, the reduction of rigidity and hardness of the cover improves controllability, but degrades rebound characteristics of the cover, thus the resulting in a golf ball not having sufficient flight performance.